The present disclosure relates to semiconductor devices, and particularly to semiconductor structures having a wide replacement gate electrode including a work function material portion, and methods of manufacturing the same.
Work function materials are employed in replacement gate electrodes to optimize the work function of field effect transistors. Most work function metals, however, have a greater resistivity than gate electrode materials such as W or Al. Thus, the thickness of the work function metal need to be controlled in a gate electrode.
A narrow gate cavity having a width less than twice the thickness of a work function material layer can be filled with the work function metal and recessed to a desired thickness. Deposition and recessing the work function metal in a wide gate cavity having a width greater than the thickness of the work function material layer, however, can cause complete removal of the work function metal from a center portion thereof. Thus, an integration scheme is desired that allows a deposited work function metal in wide gate cavities to remain in contact with the entire gate dielectric after formation of gate electrodes.